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C++ Interview Questions1. What is C++?

Released in 1985, C++ is an object-oriented programming language created by BjarneStroustrup. C++ maintains almost all aspects of the C language, while simplifyingmemory management and adding several features - including a new datatype knownas a class (you will learn more about these later) - to allow object-orientedprogramming. C++ maintains the features of C which allowed for low-level memoryaccess but also gives the programmer new tools to simplify memory management. C++ used for:C++ is a powerful general-purpose programming language. It can be used to createsmall programs or large applications. It can be used to make CGI scripts or console-only DOS programs. C++ allows you to create programs to do almost anything youneed to do. The creator of C++, Bjarne Stroustrup, has put together a partial list ofapplications written in C++.

2. How do you find out if a linked-list has an end? (i.e. the list is not acycle) You can find out by using 2 pointers. One of them goes 2 nodes each time. The secondone goes at 1 nodes each time. If there is a cycle, the one that goes 2 nodes each timewill eventually meet the one that goes slower. If that is the case, then you will knowthe linked-list is a cycle.

3. What is the difference between realloc() and free()? The free subroutine frees a block of memory previously allocated by the mallocsubroutine. Undefined results occur if the Pointer parameter is not a valid pointer. Ifthe Pointer parameter is a null value, no action will occur. The realloc subroutinechanges the size of the block of memory pointed to by the Pointer parameter to thenumber of bytes specified by the Size parameter and returns a new pointer to theblock. The pointer specified by the Pointer parameter must have been created withthe malloc, calloc, or realloc subroutines and not been deallocated with the free orrealloc subroutines. Undefined results occur if the Pointer parameter is not a valid



pointer.

4. Base class has some virtual method and derived class has a methodwith the same name. If we initialize the base class pointer with derivedobject, calling of that virtual method will result in which method beingcalled?

a. Base method b. Derived methodAns. B

5. What is function overloading and operator overloading?Function overloading: C++ enables several functions of the same name to be defined,as long as these functions have different sets of parameters (at least as far as theirtypes are concerned). This capability is called function overloading. When anoverloaded function is called, the C++ compiler selects the proper function byexamining the number, types and order of the arguments in the call. Functionoverloading is commonly used to create several functions of the same name thatperform similar tasks but on different data types.

Operator overloading allows existing C++ operators to be redefined so that they workon objects of user-defined classes. Overloaded operators are syntactic sugar forequivalent function calls. They form a pleasant facade that doesn't add anythingfundamental to the language (but they can improve understandability and reducemaintenance costs).

6. What are the advantages of inheritance? It permits code reusability. Reusability saves time in program development. Itencourages the reuse of proven and debugged high-quality software, thus reducingproblem after a system becomes functional.

7.What is the difference between declaration and definition? The declaration tells the compiler that at some later point we plan to present the



definition of this declaration.E.g.: void stars () //function declaration The definition contains the actual implementation.E.g.: void stars () // declarator{for(int j=10; j > =0; j--) //function bodycout << *;cout << endl; }

8. How do you write a function that can reverse a linked-list?

void reverselist(void){if(head==0)return;if(head->next==0)return;if(head->next==tail){head->next = 0;tail->next = head;}else{node* pre = head;node* cur = head->next;node* curnext = cur->next;head->next = 0;cur-> next = head;for(; curnext!=0; ){cur->next = pre;



pre = cur;cur = curnext;curnext = curnext->next;}

curnext->next = cur;}}

9. What do you mean by inline function?The idea behind inline functions is to insert the code of a called function at the pointwhere the function is called. If done carefully, this can improve the application'sperformance in exchange for increased compile time and possibly (but not always) anincrease in the size of the generated binary executables.

10. Write a program that ask for user input from 5 to 9 then calculate theaverage

#include "iostream.h"int main() {int MAX = 4;int total = 0;int average;int numb;for (int i=0; i<MAX; i++) {cout << "Please enter your input between 5 and 9: ";cin >> numb;while ( numb<5 || numb>9) {cout << "Invalid input, please re-enter: ";cin >> numb;}total = total + numb;}average = total/MAX;



cout << "The average number is: " << average << "\n";return 0;}

11. Write a short code using C++ to print out all odd number from 1 to 100using a for loop

for( unsigned int i = 1; i < = 100; i++ )if( i & 0x00000001 )cout << i << \",\";

12. What is public, protected, private?Public, protected and private are three access specifier in C++.Public data members and member functions are accessible outside the class.Protected data members and member functions are only available to derived classes.Private data members and member functions can’t be accessed outside the class.However there is an exception can be using friend classes.

13. Tell how to check whether a linked list is circular.Create two pointers, each set to the start of the list. Update each as follows: while(pointer1) {pointer1 = pointer1->next;pointer2 = pointer2->next; if (pointer2) pointer2=pointer2->next;if (pointer1 == pointer2) {print (\"circular\n\");}}OK, why does this work?If a list is circular, at some point pointer2 will wrap around and be either at the itemjust before pointer1, or the item before that. Either way, it’s either 1 or 2 jumps untilthey meet.

14. What is virtual constructors/destructors?Virtual destructors:If an object (with a non-virtual destructor) is destroyed explicitly



by applying the delete operator to a base-class pointer to the object, the base-classdestructor function (matching the pointer type) is called on the object.There is a simple solution to this problem declare a virtual base-class destructor. Thismakes all derived-class destructors virtual even though they don’t have the samename as the base-class destructor. Now, if the object in the hierarchy is destroyedexplicitly by applying the delete operator to a base-class pointer to a derived-classobject, the destructor for the appropriate class is called. Virtual constructor:Constructors cannot be virtual. Declaring a constructor as a virtual function is asyntax error.Virtual destructors: If an object (with a non-virtual destructor) is destroyed explicitlyby applying the delete operator to a base-class pointer to the object, the base-classdestructor function (matching the pointer type) is called on the object.There is a simple solution to this problem – declare a virtual base-class destructor.This makes all derived-class destructors virtual even though they don’t have the samename as the base-class destructor. Now, if the object in the hierarchy is destroyedexplicitly by applying the delete operator to a base-class pointer to a derived-classobject, the destructor for the appropriate class is called.Virtual constructor: Constructors cannot be virtual. Declaring a constructor as avirtual function is a syntax error.

15. Does c++ support multilevel and multiple inheritance?Yes.

16. What are the advantages of inheritance?• It permits code reusability.• Reusability saves time in program development.• It encourages the reuse of proven and debugged high-quality software, thusreducing problem after a system becomes functional.

17. What is the difference between declaration and definition?The declaration tells the compiler that at some later point we plan to present thedefinition of this declaration.E.g.: void stars () //function declaration



The definition contains the actual implementation.E.g.: void stars () // declarator{for(int j=10; j>=0; j--) //function bodycout<<”*”;cout<<endl; }

18. What is the difference between an array and a list?

Array is collection of homogeneous elements. List is collection of heterogeneouselements.For Array memory allocated is static and continuous. For List memory allocated isdynamic and Random.Array: User need not have to keep in track of next memory allocation.List: User has to keep in Track of next location where memory is allocated.Array uses direct access of stored members, list uses sequencial access for members./With Array you have direct access to memory position 5Object x = a[5]; // x takes directly a reference to 5th element of array//With the list you have to cross all previous nodes in order to get the 5th node:list mylist;list::iterator it;for( it = list.begin() ; it != list.end() ; it++ ){if( i==5){x = *it;break;}i++;}

19. What is a template?



Templates allow to create generic functions that admit any data type as parametersand return value without having to overload the function with all the possible datatypes. Until certain point they fulfill the functionality of a macro. Its prototype is anyof the two following ones:template <class indetifier> function_declaration; template <typename indetifier>function_declaration;The only difference between both prototypes is the use of keyword class or typename,its use is indistinct since both expressions have exactly the same meaning and behaveexactly the same way.

20. Define a constructor - What it is and how it might be called (2methods).Constructor is a member function of the class, with the name of the function being thesame as the class name. It also specifies how the object should be initialized.Ways of calling constructor:1) Implicitly: automatically by complier when an object is created.2) Calling the constructors explicitly is possible, but it makes the code unverifiable.class Point2D{int x; int y;public Point2D() : x(0) , y(0) {} //default (no argument) constructor};main(){Point2D MyPoint; // Implicit Constructor call. In order to allocate memory on stack,the default constructor is implicitly called.Point2D * pPoint = new Point2D(); // Explicit Constructor call. In order to allocatememory on HEAP we call the default constructor. You have two pairs: new() and delete() and another pair : alloc() and free().

21. Explain differences between eg. new() and malloc()1.) “new and delete” are preprocessors while “malloc() and free()” are functions. [wedont use brackets will calling new or delete].2.) no need of allocate the memory while using “new” but in “malloc()” we have to use“sizeof()”.



3.) “new” will initlize the new memory to 0 but “malloc()” gives random value in thenew alloted memory location [better to use calloc()]new() allocates continous space for the object instace malloc() allocates distributedspace.new() is castless, meaning that allocates memory for this specific type,malloc(), calloc() allocate space for void * that is cated to the specific class typepointer.

22. What is the difference between class and structure?Structure: Initially (in C) a structure was used to bundle different type of data typestogether to perform a particular functionality. But C++ extended the structure tocontain functions also. The major difference is that all declarations inside a structureare by default public.Class: Class is a successor of Structure. By default all the members inside the class areprivate.

23. What is RTTI?Runtime type identification (RTTI) lets you find the dynamic type of an object whenyou have only a pointer or a reference to the base type. RTTI is the official way instandard C++ to discover the type of an object and to convert the type of a pointer orreference (that is, dynamic typing).

24.What is encapsulation?Packaging an object’s variables within its methods is called encapsulation.

25.Explain term “Polymorphism” and give an example using eg. SHAPE object:If I have a base class SHAPE, how would I define DRAW methods for two objectsCIRCLE and SQUARE“Polymorphism”: A phenomenon which enables an object toreact differently to the same function call. in C++ it is attained by using a keywordvirtualExamplepublic class SHAPE{public virtual void SHAPE::DRAW()=0;



}Note here the function DRAW() is pure virtual which means the sub classes mustimplement the DRAW() method and SHAPE cannot be instatiatedpublic class CIRCLE::public SHAPE{public void CIRCLE::DRAW(){// TODO drawing circle}}public class SQUARE::public SHAPE{public void SQUARE::DRAW(){// TODO drawing square}}

now from the user class the calls would be like globallySHAPE *newShape;When user action is to drawpublic void MENU::OnClickDrawCircle(){newShape = new CIRCLE();}

public void MENU::OnClickDrawCircle(){newShape = new SQUARE();}

the when user actually drawspublic void CANVAS::OnMouseOperations(){newShape->DRAW();}



class SHAPE{public virtual Draw() = 0; //abstract class with a pure virtual method};class CIRCLE{public int r;public virtual Draw() { this->drawCircle(0,0,r); }};

class SQUREpublic int a;public virtual Draw() { this->drawRectangular(0,0,a,a); }};Each object is driven down from SHAPE implementing Draw() function in its ownway.

26. What is an object?Object is a software bundle of variables and related methods. Objects have state andbehavior.

27. How can you tell what shell you are running on UNIX system?You can do the Echo $RANDOM. It will return a undefined variable if you are fromthe C-Shell, just a return prompt if you are from the Bourne shell, and a 5 digitrandom numbers if you are from the Korn shell. You could also do a ps -l and look forthe shell with the highest PID.

28. What do you mean by inheritance?Inheritance is the process of creating new classes, called derived classes, from existingclasses or base classes. The derived class inherits all the capabilities of the base class,but can add embellishments and refinements of its own.

29.Describe PRIVATE, PROTECTED and PUBLIC – the differences andgive examples.class Point2D{int x; int y;



public int color;protected bool pinned;public Point2D() : x(0) , y(0) {} //default (no argument) constructor};Point2D MyPoint;You cannot directly access private data members when they are declared (implicitly)private:MyPoint.x = 5; // Compiler will issue a compile ERROR//Nor yoy can see them:int x_dim = MyPoint.x; // Compiler will issue a compile ERROR

On the other hand, you can assign and read the public data members:MyPoint.color = 255; // no problemint col = MyPoint.color; // no problemWith protected data members you can read them but not write them: MyPoint.pinned= true; // Compiler will issue a compile ERRORbool isPinned = MyPoint.pinned; // no problem

30. What is namespace?Namespaces allow us to group a set of global classes, objects and/or functions under aname. To say it somehow, they serve to split the global scope in sub-scopes known asnamespaces.The form to use namespaces is:namespace identifier { namespace-body }Where identifier is any valid identifier and namespace-body is the set of classes,objects and functions that are included within the namespace. For example:namespace general { int a, b; } In this case, a and b are normal variables integratedwithin the general namespace. In order to access to these variables from outside thenamespace we have to use the scope operator ::. For example, to access the previousvariables we would have to put:general::a general::bThe functionality of namespaces is specially useful in case that there is a possibilitythat a global object or function can have the same name than another one, causing a



redefinition error.

31. What is a COPY CONSTRUCTOR and when is it called?A copy constructor is a method that accepts an object of the same class and copies it’sdata members to the object on the left part of assignment:class Point2D{int x; int y;public int color;protected bool pinned;public Point2D() : x(0) , y(0) {} //default (no argument) constructorpublic Point2D( const Point2D & ) ;};Point2D::Point2D( const Point2D & p ){this->x = p.x;this->y = p.y;this->color = p.color;this->pinned = p.pinned;}

main(){Point2D MyPoint;MyPoint.color = 345;Point2D AnotherPoint = Point2D( MyPoint ); // now AnotherPoint has color = 345

32. What is Boyce Codd Normal form?A relation schema R is in BCNF with respect to a set F of functional dependencies iffor all functional dependencies in F+ of the form a-> , where a and b is a subset of R,at least one of the following holds:* a- > b is a trivial functional dependency (b is a subset of a)* a is a superkey for schema R

33. What is virtual class and friend class?Friend classes are used when two or more classes are designed to work together and



need access to each other's implementation in ways that the rest of the worldshouldn't be allowed to have. In other words, they help keep private things private.For instance, it may be desirable for class DatabaseCursor to have more privilege tothe internals of class Database than main() has.

34. What is the word you will use when defining a function in base class toallow this function to be a polimorphic function?

virtual

35. What do you mean by binding of data and functions?

Encapsulation.

36. What are 2 ways of exporting a function from a DLL?

1. Taking a reference to the function from the DLL instance.2. Using the DLL ’s Type Library

37. What is the difference between an object and a class?

Classes and objects are separate but related concepts. Every object belongs to a classand every class contains one or more related objects.- A Class is static. All of the attributes of a class are fixed before, during, and after theexecution of a program. The attributes of a class don't change.- The class to which an object belongs is also (usually) static. If a particular objectbelongs to a certain class at the time that it is created then it almost certainly will stillbelong to that class right up until the time that it is destroyed.- An Object on the other hand has a limited lifespan. Objects are created andeventually destroyed. Also during that lifetime, the attributes of the object mayundergo significant change.

38. What is a class?

Class is a user-defined data type in C++. It can be created to solve a particular kind ofproblem. After creation the user need not know the specifics of the working of a class.



39. What is friend function?

As the name suggests, the function acts as a friend to a class. As a friend of a class, itcan access its private and protected members. A friend function is not a member ofthe class. But it must be listed in the class definition.

40. Which recursive sorting technique always makes recursive calls tosort subarrays that are about half size of the original array?

Mergesort always makes recursive calls to sort subarrays that are about half size ofthe original array, resulting in O(n log n) time.

41. What is abstraction?

Abstraction is of the process of hiding unwanted details from the user.

42. What are virtual functions?

A virtual function allows derived classes to replace the implementation provided bythe base class. The compiler makes sure the replacement is always called wheneverthe object in question is actually of the derived class, even if the object is accessed by abase pointer rather than a derived pointer. This allows algorithms in the base class tobe replaced in the derived class, even if users don't know about the derived class.

43.What is the difference between an external iterator and an internaliterator? Describe an advantage of an external iterator.

An internal iterator is implemented with member functions of the class that has itemsto step through. .An external iterator is implemented as a separate class that can be"attach" to the object that has items to step through. .An external iterator has theadvantage that many difference iterators can be active simultaneously on the sameobject.

44. What is a scope resolution operator?A scope resolution operator (::), can be used to define the member functions of a classoutside the class.



45. What do you mean by pure virtual functions?

A pure virtual member function is a member function that the base class forcesderived classes to provide. Normally these member functions have noimplementation. Pure virtual functions are equated to zero.class Shape { public: virtual void draw() = 0; };

46. What is polymorphism? Explain with an example?

"Poly" means "many" and "morph" means "form". Polymorphism is the ability of anobject (or reference) to assume (be replaced by) or become many different forms ofobject.Example: function overloading, function overriding, virtual functions. Anotherexample can be a plus ‘+’ sign, used for adding two integers or for using it toconcatenate two strings.

47.What’s the output of the following program? Why?

#include <stdio.h>main(){typedef union{int a;char b[10];float c;}Union;Union x,y = {100};x.a = 50;strcpy(x.b,\"hello\");x.c = 21.50;printf(\"Union x : %d %s %f \n\",x.a,x.b,x.c );printf(\"Union y :%d %s%f \n\",y.a,y.b,y.c);



}Given inputs X, Y, Z and operations | and & (meaning bitwise OR and AND,respectively)What is output equal to inoutput = (X & Y) | (X & Z) | (Y & Z)

48. Why arrays are usually processed with for loop?

The real power of arrays comes from their facility of using an index variable totraverse the array, accessing each element with the same expression a[i]. All the isneeded to make this work is a iterated statement in which the variable i serves as acounter, incrementing from 0 to a.length -1. That is exactly what a loop does.

49. What is an HTML tag?

An HTML tag is a syntactical construct in the HTML language that abbreviatesspecific instructions to be executed when the HTML script is loaded into a Webbrowser. It is like a method in Java, a function in C++, a procedure in Pascal, or asubroutine in FORTRAN.

50.Explain which of the following declarations will compile and what willbe constant - a pointer or the value pointed at: * const char ** char const ** char * const

51. What problems might the following macro bring to the application?

#define sq(x) x*x

52. Anything wrong with this code?

T *p = new T[10];delete p;Everything is correct, Only the first element of the array will be deleted”, The entirearray will be deleted, but only the first element destructor will be called.



53. Anything wrong with this code?

T *p = 0;delete p;Yes, the program will crash in an attempt to delete a null pointer.

54. How do you decide which integer type to use?

It depends on our requirement. When we are required an integer to be stored in 1 byte(means less than or equal to 255) we use short int, for 2 bytes we use int, for 8 byteswe use long int.A char is for 1-byte integers, a short is for 2-byte integers, an int is generally a 2-byteor 4-byte integer (though not necessarily), a long is a 4-byte integer, and a long long isa 8-byte integer.

55. What does extern mean in a function declaration?

Using extern in a function declaration we can make a function such that it can usedoutside the file in which it is defined.An extern variable, function definition, or declaration also makes the describedvariable or function usable by the succeeding part of the current source file. Thisdeclaration does not replace the definition. The declaration is used to describe thevariable that is externally defined.If a declaration for an identifier already exists at file scope, any extern declaration ofthe same identifier found within a block refers to that same object. If no otherdeclaration for the identifier exists at file scope, the identifier has external linkage.

56. What can I safely assume about the initial values of variables whichare not explicitly initialized?

It depends on complier which may assign any garbage value to a variable if it is notinitialized.

57. What is the difference between char a[] = “string”; and char *p =“string”;?



In the first case 6 bytes are allocated to the variable a which is fixed, where as in thesecond case if *p is assigned to some other value the allocate memory can change.

58. What’s the auto keyword good for?Not much. It declares an object with automatic storage duration. Which means theobject will be destroyed at the end of the objects scope. All variables in functions thatare not declared as static and not dynamically allocated have automatic storageduration by default.For exampleint main(){int a; //this is the same as writing “auto int a;”}Local variables occur within a scope; they are “local” to a function. They are oftencalled automatic variables because they automatically come into being when the scopeis entered and automatically go away when the scope closes. The keyword auto makesthis explicit, but local variables default to auto auto auto auto so it is never necessaryto declare something as an auto auto auto auto.

59. What is the difference between char a[] = “string”; and char *p =“string”; ?

a[] = “string”;char *p = “string”;The difference is this:p is pointing to a constant string, you can never safely sayp[3]=’x';however you can always say a[3]=’x';char a[]=”string”; - character array initialization.char *p=”string” ; - non-const pointer to a const-string.( this is permitted only in thecase of char pointer in C++ to preserve backward compatibility with C.)

60. How do I declare an array of N pointers to functions returningpointers to functions returning pointers to characters?



If you want the code to be even slightly readable, you will use typedefs.typedef char* (*functiontype_one)(void);typedef functiontype_one (*functiontype_two)(void);functiontype_two myarray[N]; //assuming N is a const integral

61. What does extern mean in a function declaration?It tells the compiler that a variable or a function exists, even if the compiler hasn’t yetseen it in the file currently being compiled. This variable or function may be definedin another file or further down in the current file.

62. How do I initialize a pointer to a function?

This is the way to initialize a pointer to a functionvoid fun(int a){}void main(){void (*fp)(int);fp=fun;fp(1);}

63. How do you link a C++ program to C functions?

By using the extern "C" linkage specification around the C function declarations.

64. Explain the scope resolution operator.

It permits a program to reference an identifier in the global scope that has beenhidden by another identifier with the same name in the local scope.

65. What are the differences between a C++ struct and C++ class?The default member and base-class access specifier are different.

66. How many ways are there to initialize an int with a constant?



Two. There are two formats for initializers in C++ as shown in the example thatfollows. The first format uses the traditional C notation. The second format usesconstructor notation.int foo = 123;int bar (123);

67. How does throwing and catching exceptions differ from using setjmpand longjmp?

The throw operation calls the destructors for automatic objects instantiated sinceentry to the try block.

68. What is a default constructor?

Default constructor WITH arguments class B { public: B (int m = 0) : n (m) {} int n; };int main(int argc, char *argv[]) { B b; return 0; }

69. What is a conversion constructor?A constructor that accepts one argument of a different type.

70. What is the difference between a copy constructor and an overloadedassignment operator?

A copy constructor constructs a new object by using the content of the argumentobject. An overloaded assignment operator assigns the contents of an existing objectto another existing object of the same class.

71. When should you use multiple inheritance?

There are three acceptable answers: "Never," "Rarely," and "When the problemdomain cannot be accurately modeled any other way."

72. Explain the ISA and HASA class relationships. How would youimplement each in a class design?

A specialized class "is" a specialization of another class and, therefore, has the ISA



relationship with the other class. An Employee ISA Person. This relationship is bestimplemented with inheritance. Employee is derived from Person. A class may have aninstance of another class. For example, an employee "has" a salary, therefore theEmployee class has the HASA relationship with the Salary class. This relationship isbest implemented by embedding an object of the Salary class in the Employee class.

73. When is a template a better solution than a base class?

When you are designing a generic class to contain or otherwise manage objects ofother types, when the format and behavior of those other types are unimportant totheir containment or management, and particularly when those other types areunknown (thus, the generosity) to the designer of the container or manager class.

74. What is a mutable member?

One that can be modified by the class even when the object of the class or the memberfunction doing the modification is const.

75. What is an explicit constructor?

A conversion constructor declared with the explicit keyword. The compiler does notuse an explicit constructor to implement an implied conversion of types. It’s purposeis reserved explicitly for construction.

76. What is the Standard Template Library (STL)?

A library of container templates approved by the ANSI committee for inclusion in thestandard C++ specification. A programmer who then launches into a discussion of thegeneric programming model, iterators, allocators, algorithms, and such, has a higherthan average understanding of the new technology that STL brings to C++programming.

77. Describe run-time type identification.

The ability to determine at run time the type of an object by using the typeid operatoror the dynamic cast operator.



78. What problem does the namespace feature solve?

Multiple providers of libraries might use common global identifiers causing a namecollision when an application tries to link with two or more such libraries. Thenamespace feature surrounds a library’s external declarations with a uniquenamespace that eliminates the potential for those collisions.This solution assumes that two library vendors don’t use the same namespaceidentifier, of course.

79. Are there any new intrinsic (built-in) data types?

Yes. The ANSI committee added the bool intrinsic type and its true and false valuekeywords.

80. Will the following program execute?void main(){void *vptr = (void *) malloc(sizeof(void));vptr++;}It will throw an error, as arithmetic operations cannot be performed on void pointers.

81. For the following C program

#define AREA(x)(3.14*x*x)main(){float r1=6.25,r2=2.5,a;a=AREA(r1);printf("\n Area of the circle is %f", a);a=AREA(r2);printf("\n Area of the circle is %f", a);}What is the output?



Ans. Area of the circle is 122.656250Area of the circle is 19.625000

82. void main()

{int d=5;printf("%f",d);}Ans: Undefined

83. void main(){int i;for(i=1;i<4,i++)switch(i)case 1: printf("%d",i);break;{case 2:printf("%d",i);break;case 3:printf("%d",i);break;}switch(i) case 4:printf("%d",i);}Ans: 1,2,3,4

84.void main(){char *s="\12345s\n";printf("%d",sizeof(s));}Ans: 6

85.void main(){



unsigned i=1; /* unsigned char k= -1 => k=255; */signed j=-1; /* char k= -1 => k=65535 *//* unsigned or signed int k= -1 =>k=65535 */if(i<j)printf("less");elseif(i>j)printf("greater");elseif(i==j)printf("equal");}Ans: less</j)

86. void main(){float j;j=1000*1000;printf("%f",j);}1. 10000002. Overflow3. Error4. None Ans: 4

87. How do you declare an array of N pointers to functions returning pointers to functions returning pointers to characters?

Ans: The first part of this question can be answered in at least three ways:1. char *(*(*a[N])())();2. Build the declaration up incrementally, using typedefs:typedef char *pc; /* pointer to char */



typedef pc fpc(); /* function returning pointer to char */typedef fpc *pfpc; /* pointer to above */typedef pfpc fpfpc(); /* function returning... */typedef fpfpc *pfpfpc; /* pointer to... */pfpfpc a[N]; /* array of... */3. Use the cdecl program, which turns English into C and vice versa:cdecl> declare a as array of pointer to function returning pointer to function returningpointer to charchar *(*(*a[])())()

88.What is a modifier?

A modifier, also called a modifying function is a member function that changes thevalue of at least one data member. In other words, an operation that modifies thestate of an object. Modifiers are also known as ‘mutators’.

89.What is an accessor?

An accessor is a class operation that does not modify the state of an object. Theaccessor functions need to be declared as const operations

90.Differentiate between a template class and class template.

Template class: A generic definition or a parameterized class not instantiated until theclient provides the needed information. It’s jargon for plain templates.

Class template: A class template specifies how individual classes can be constructedmuch like the way class specifies how individual objects can be constructed. It’sjargon for plain classes

91.When does a name clash occur?

A name clash occurs when a name is defined in more than one place. For example.,two different class libraries could give two different classes the same name. If you tryto use many class libraries at the same time, there is a fair chance that you will beunable to compile or link the program because of name clashes.



92.What is a dangling pointer?

A dangling pointer arises when you use the address of an object after its lifetime isover. This may occur in situations like returning addresses of the automatic variablesfrom a function or using the address of the memory block after it is freed.

93.Differentiate between the message and method.

Message:

Objects communicate by sending messages to each other.A message is sent to invoke a method

Method:

Provides response to a message.It is an implementation of an operation.

94.What is an adaptor class or Wrapper class?

A class that has no functionality of its own. Its member functions hide the use of athird party software component or an object with the non-compatible interface or anon-object-oriented implementation.

95.What is a Null object?

It is an object of some class whose purpose is to indicate that a real object of that classdoes not exist. One common use for a null object is a return value from a memberfunction that is supposed to return an object with some specified properties butcannot find such an object.

96.What is class invariant? A class invariant is a condition that defines all valid states for an object. It is a logicalcondition to ensure the correct working of a class. Class invariants must hold when anobject is created, and they must be preserved under all operations of the class. Inparticular all class invariants are both preconditions and post-conditions for all



operations or member functions of the class.

97.What do you mean by Stack unwinding?

It is a process during exception handling when the destructor is called for all localobjects between the place where the exception was thrown and where it is caught.

98.What are proxy objects?

Objects that stand for other objects are called proxy objects or surrogates.

99.Name some pure object oriented languages.

Smalltalk, Java, Eiffel, Sather.

100.What is an orthogonal base class?

If two base classes have no overlapping methods or data they are said to beindependent of, or orthogonal to each other. Orthogonal in the sense means that twoclasses operate in different dimensions and do not interfere with each other in anyway. The same derived class may inherit such classes with no difficulty.

101.What is the difference between Mutex and Binary semaphore?

semaphore is used to synchronize processes. where as mutex is used to providesynchronization between threads running in the same process

102.What is destructor?

Destructor usually deletes any extra resources allocated by the object.

103.What are C++ storage classes?

autoregisterstaticextern



auto:the default. Variables are automatically created and initialized when they aredefined and are destroyed at the end of the block containing their definition. They arenot visible outside that blockregister:a type of auto variable. a suggestion to the compiler to use a CPU register forperformancestatic:a variable that is known only in the function that contains its definition but isnever destroyed and retains its value between calls to that function. It exists from thetime the program begins executionextern:a static variable whose definition and placement is determined when all objectand library modules are combined (linked) to form the executable code file. It can bevisible outside the file where it is defined.

104.What is reference ?

reference is a name that acts as an alias, or alternative name, for a previously definedvariable or an object.prepending variable with "&" symbol makes it as reference.for example: int a;int &b = a;

105.What are the defining traits of an object-oriented language?

The defining traits of an object-oriented langauge are:encapsulationinheritancepolymorphism

106.What is Quadratic Probing?

The Performance problem encountered by linear probing is caused by the clusterbuildup That occurs as a result of the probing sequence. Quadratic probing uses adifferent sequence to avoid primary clustering.

107.What is the chaining?



The Chaining technique basically looks at the hash table as an array of pointers tolinked lists. Each slot in the hash table is either empty or simply consists of a pointerto a linked list. You resolve collisions by adding the elements that hash to the sameslot to the linked list to which that slot points. At the same time, deletions are easy,You simply delete elements from the linked list.

108.What is the Hash Function?

The hash function is an important part of the hashing technique. This function is usedto transform the keys into table addresses. The hash function we choose should beeasy to compute and should be able to transform the keys into integers in the range 0to TR-1. Because most of the commonly used hash functions are based on arithmeticoperations, We should convert the keys to numbers on which arithmetic operationscan be performed

109.What is an Visualizations?

The visualization is the basically a way of presentation ,Its just a fancy name for thediagrams, pictures, screen shots, prototypes, and any other visual representationscreated to help through and design the graphical user interface of your product.

110.What is virtual inheritance?

Inheritance is a basically can be private , public, or virtual. With virtual inheritancethere is only one copy of each object even if the object appears more than once in thehierarchy.

111.What is multithreading

Multithreading is defined as :It is the task of creating a new thread of executionwithin an existing process rather than starting a new process to begin a function. It isthe ability of an operating system to concurrently run programs that have beendivided into subcomponents, or threads.

112.What is the use of using?



Using is bassically a namespace scope. Its directive used to declare the accessibility ofidentifiers declared within a namespace scope.

113.What is the use of exception handling?

Exception handling is bassically used to detect exceptions becouse it can be taken acorresponding action

114.What is EOF?

EOF bassically stands for End of File, It is used to check for the end of file when a fileis being read.

115.Define the parameterized macros?

Parameterized macros are use for the parameters . It is the one which consist oftemplate with insertion points for the addition of parameters.

116.What is overflow error?

Overflow error basically a type of arithmatic errors.It's caused by the result of anarithmetic operation being greater than the actual space provided by the system.

117.What is a nested class? Why can it be useful?Nested classes basically useful for organizing code and controlling access anddependencies. Nested classes obey access rules just like other parts of a class do.andthat class is a class enclosed within the scope of another class.

118.What are the disadvantages of C++?

a)It's not pure object oriented programming language.

b)Its a Platform dependentc)C++ does not give excellant graphics as compare to java.d)Its Not case sensitive.e)C++ have Less features as comapred to Java& C#.f)Its Not applicable in web enviornment.



g)Does not provide very strong type-checking. h)c++ code is easily prone to errors related to data types, their conversions.i)Does not provide efficient means for garbage collection. j)No built in support for threads

119.What is an iterator?

An iterator is a bassically a type of object that represents a stream of data. It is Unlikea sequence, an iterator can only provide the next item. The for-in statement usesiterators to control the loop, and iterators can also be used in many other contexts

120.What is the Auto Storage Class?

Auto Storage Class is bassically the default. Variables are automatically created andinitialized, When they are defined and are destroyed at the end of the blockcontaining their definition. They are not visible outside that block.

121.What is callback function?

Callback function is the type of pointer for a function

122.What is the use of tellg ()?

tellg () provides a information about the current position of input/get pointer.

123.What is the use of tellp ()?

tellp ()use for the poitner postion :Its provides the current position of output/putpointer

124.Define the generic programming?

Generic Programmng is type of method. The method in which generic types are usedas arguments in algorithms for different data types and data structures is calledgeneric programming.

125.What is the use of Microsoft foundation class library?



The Microsoft Foundation Class Library also called as A Microsoft Foundation Classesor MFC. It is basically a library that wraps portions of the Windows API in C++classes, and including functionality that enables them to use a default applicationframework. Classes are defined for many of the handle-managed Windows objectsand also for predefined windows and common controls. MFC library would help usreduce the code and development time.

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